Method for controlling ion concentration and volume balance in electrolyte by using nickel hydroxide

Abstract

The present application discloses a method for controlling ion concentration and volume balance in an electrolyte by using nickel hydroxide, comprising the following steps: preparing a reaction mother liquor containing a first complexing agent and a first alkali; simultaneously adding a first anolyte, a second complexing agent solution, and a second alkali solution to the bottom of the reaction mother liquor for stirring reaction, and when nickel hydroxide reaches a target particle size, performing solid-liquid separation to obtain a filtrate and a filter cake; washing the filter cake, and then using a second anolyte for slurrying to obtain a nickel hydroxide slurry; and using a sodium hydroxide solution, the nickel hydroxide slurry, and a nickel sulfate solution to adjust the sodium ion concentration, pH and nickel ion concentration of a third anolyte to obtain a catholyte. In the present application, crystals can be stably grown and conveniently filtered by using a bottom feeding mode in combination with complexing agents. Aging and excessively high pH conditions are not required in the preparation process of the present application, so that the operation is simpler, the labor intensity is lower, the reaction rate is higher, and continuous treatment of anolytes can be implemented.

Description

Method for controlling ion concentration and volume balance in electrolyte using nickel hydroxide Technical Field

[0001] This application relates to the field of nickel electrolysis technology, and in particular to a method for controlling the ion concentration and volume balance in an electrolyte using nickel hydroxide. Background Technology

[0002] Nickel electrolysis is a process in which an external power source supplies electricity to the electrolytic cell, and under the influence of current, nickel ions are reduced to metallic nickel at the cathode. During nickel electrolysis, the electrolyte circulation is a closed-loop system: the cathode electrolyte (i.e., catholyte) permeates through the diaphragm to the anode chamber, and the anolyte (i.e., anolyte) returns to the cathode chamber after purification. To maintain long-term normal production, the total volume of circulating electrolyte in the entire system must remain approximately constant. However, during production, the electrolyte volume often changes. Reasons for electrolyte volume reduction include: water carried away by electrolyte evaporation, water carried away by the produced slag, and some electrolyte extracted during nickel carbonate preparation. Reasons for electrolyte volume expansion include: water introduced by the replenishment of nickel sulfate solution, water introduced by the reagents added during purification, and backflushing water in the pipeline. In actual production, the chance of electrolyte volume expansion is much greater than the chance of volume reduction, especially water introduced by the replenishment of nickel sulfate solution. Improper operation control can lead to rapid electrolyte volume expansion. Therefore, the volume of water introduced and the volume of electrolyte extracted during nickel carbonate preparation must be strictly controlled during production to regulate the total electrolyte volume. During nickel electrolysis, a certain concentration of sodium ions can improve the conductivity of the electrolyte, reduce the solution resistance, and decrease power consumption. However, excessively high sodium ion concentrations not only increase the internal stress of the cathode nickel, causing nickel plate peeling and bending, but may also exacerbate electrode polarization. Furthermore, excessively high sodium ion concentrations will increase the viscosity of the solution and the resistance of the diaphragm bag, affecting filtration performance, causing crystallization, clogging pipes and valves, and disrupting normal production. However, because sodium carbonate solution is used to adjust the pH of the electrolyte during purification, the sodium ion concentration in the electrolyte will gradually increase. To maintain the sodium ion concentration in the electrolyte within a certain range, a certain amount of sodium salt must be periodically removed from the production system. Currently, a common method for removing sodium salts involves extracting a portion of the anolyte from a closed-loop electrolyte circulation system. The nickel sulfate in the anolyte reacts with sodium carbonate to produce nickel carbonate and sodium sulfate. The nickel carbonate is then returned to the electrolyte circulation system as a neutralizing agent. The solution after nickel carbonate precipitation contains a large amount of sulfate ions, sodium ions, and water, which is discarded to achieve sulfur balance, sodium balance, and volume balance in the production system. The chemical reaction equations involved in this process include: NiSO4 + Na2CO3 = NiCO3↓ + Na2SO4 NiCO3 + 2H+ + =Ni 2+ +H₂O + CO₂↑

[0003] However, existing methods for controlling ion concentration and volume balance using nickel carbonate suffer from incomplete precipitation reactions due to the large solubility product of nickel carbonate. This results in high nickel content in the filtered wastewater after precipitation, making wastewater treatment more difficult. To ensure a more complete reaction, an aging process is often required, which complicates the process and increases labor intensity. Furthermore, the use of a parallel inlet flow of raw material and alkali solutions during sodium carbonate addition leads to excessively high reactant concentrations, causing the precipitation reaction to occur instantaneously and generating numerous crystal nuclei. The rapid nucleus formation rate contrasts sharply with the slow crystal growth rate, easily producing difficult-to-filter colloidal solids and basic carbonates, resulting in fluctuations in the quality of electrolytic nickel products. In addition, existing nickel carbonate production processes operate at a high temperature of 85°C, which is unsuitable for long-term operation of instruments and equipment.

[0004] Therefore, there is an urgent need to provide a new method for controlling the ion concentration and volume balance in the electrolyte to solve the above problems. Summary of the Invention

[0005] The purpose of this application is to overcome the above-mentioned technical deficiencies and propose a method for controlling the ion concentration and volume balance in the electrolyte using nickel hydroxide, thereby solving the technical problems of complex process, high labor intensity, and difficulty in filtering nickel carbonate slurry in the existing method for controlling ion concentration and volume balance using nickel carbonate.

[0006] This application provides a method for controlling the ion concentration and volume balance in an electrolyte using nickel hydroxide, comprising the following steps:

[0007] S1. Prepare a reaction base solution containing the first complexing agent and the first base;

[0008] S2. The first anolyte, the second complexing agent solution, and the second alkaline solution are simultaneously added to the bottom of the reaction substrate and stirred to react. After the nickel hydroxide reaches the target particle size, solid-liquid separation is performed to obtain filtrate and filter cake.

[0009] S3. After washing the filter cake, it is slurried with the second anolyte to obtain nickel hydroxide slurry.

[0010] S4. The sodium ion concentration, pH, and nickel ion concentration of the third anolyte are adjusted using sodium hydroxide solution, nickel hydroxide slurry, and nickel sulfate solution to obtain the catholyte.

[0011] Compared with the prior art, the beneficial effects of this application include:

[0012] This application employs a bottom-feeding method, combined with a complexing agent, which enables stable crystal growth and facilitates filtration. The preparation process of this application does not require aging or excessively high pH conditions, making the operation simpler, reducing labor intensity, increasing the reaction rate, and enabling continuous preparation of nickel hydroxide and continuous treatment of anolyte. Attached Figure Description

[0013] Figure 1 is a process flow diagram of one embodiment of the method for controlling ion concentration and volume balance in electrolyte using nickel hydroxide provided by the present invention. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0015] Please refer to Figure 1. This application provides a method for controlling the ion concentration and volume balance in an electrolyte using nickel hydroxide, comprising the following steps:

[0016] S1. Prepare a reaction base solution containing the first complexing agent and the first base;

[0017] S2. The first anolyte, the second complexing agent solution, and the second alkaline solution are simultaneously added to the bottom of the reaction substrate and stirred to react. After the nickel hydroxide reaches the target particle size, solid-liquid separation is performed to obtain filtrate and filter cake.

[0018] S3. After washing the filter cake, it is slurryed with a second anolyte to obtain nickel hydroxide slurry. In this step, washing the filter cake can remove impurities such as sodium ions and complexing agents carried in the filter cake.

[0019] S4. The sodium ion concentration, pH, and nickel ion concentration of the third anolyte are adjusted using sodium hydroxide solution, nickel hydroxide slurry, and nickel sulfate solution to obtain the catholyte.

[0020] This application utilizes nickel hydroxide to control the ion concentration and volume balance in the electrolyte. Specifically, regarding ion concentration balance, the nickel ions consumed during nickel electrolysis are replenished by nickel hydroxide slurry and a high-concentration nickel sulfate solution, thus achieving a balance in nickel ion concentration. However, due to the replenishment of the high-concentration nickel sulfate and sodium hydroxide solutions, as well as the electrolysis of water during electrowinning, the concentrations of sodium ions, hydrogen ions, and sulfate ions in the anolyte continuously increase. Hydrogen ions are neutralized by the acid-base relationship of nickel hydroxide, and excess sodium sulfate is discharged along with high-concentration sodium sulfate wastewater (filtrate after solid-liquid separation) during the preparation of nickel hydroxide, thus achieving a balance in sulfate and sodium ion concentrations. Regarding volume balance, the replenished high-concentration nickel sulfate solution introduces a large amount of water, and excess water is also discharged along with high-concentration sodium sulfate wastewater during the preparation of nickel hydroxide, thus achieving volume balance. The reactions occurring at the cathode and anode during electrowinning are as follows:

[0021] Cathode: Ni 2+ +2e - =Ni

[0022] anode:

[0023] This application utilizes a complexing agent to facilitate rapid particle growth of nickel hydroxide. Without a complexing agent, the reaction rate is slow, hindering rapid reaction and resulting in fewer particles meeting the target size range. Specifically, the formation of spherical nickel hydroxide involves three processes: nucleation, crystal growth, and aggregation. Nucleation and crystal growth determine the size of the nickel hydroxide crystallites. A rapid nucleation rate coupled with a slow crystal growth rate results in a gel-like solid, while a rapid growth rate leads to large crystals. Compared to conventional nickel hydroxide production processes, this application's method, by adding a complexing agent, first allows Ni... 2+ It forms a complex with a complexing agent, and then the complex reacts with hydroxide ions in the solution to form a precipitate. In this process, the formation of the complex significantly reduces the free Ni... 2+ The concentration of Ni in the material was adjusted, and thorough stirring further reduced the concentration of Ni. 2+ Rapid dilution. Both of these factors contribute to the precipitation reaction of Ni ions. 2+ The supersaturation decreases. Since the nucleation rate v is proportional to the supersaturation S of the reactants forming the crystals, this controls the nucleation rate to prevent it from becoming too fast and avoids the formation of colloidal precipitates. Simultaneously, intense stirring causes the microcrystals to quickly aggregate into spherical aggregates, and the shear force prevents the aggregated particles from becoming too large, ultimately yielding a nickel hydroxide product with a moderate particle size distribution and easy solid-liquid separation. Taking ammonia as a complexing agent as an example, the relevant reaction formulas in the nickel hydroxide preparation process are: Ni 2+ +xNH3·H2O=[Ni(NH3) x ] 2++xH2O [Ni(NH3) x ] 2+ +2OH - =Ni(OH)2 + xNH3

[0024] Compared with existing methods that use nickel carbonate to control ion concentration and volume balance, nickel hydroxide has a smaller solubility product, a more thorough reaction, less nickel in the wastewater, and lower wastewater treatment pressure. This application adopts a bottom feeding method and uses a complexing agent to prevent the initial reaction concentration from being too high, which allows the crystals to grow stably and is easy to filter.

[0025] Compared with existing methods that use nickel carbonate to control ion concentration and volume balance, this application uses nickel hydroxide to adjust the pH of the anolyte. No CO2 gas is generated during the reaction, so there is no need to install a special CO2 collection device in the reactor, and the risk of leakage caused by the generation of a large amount of CO2 gas is also avoided.

[0026] Compared with other existing methods for controlling ion concentration and volume balance, the method of this application can guarantee the stability of each reactor (reactor volume 36m³) after the reaction stabilizes. 3 (At time) Anode liquid feed at 6m 3 It has a significant speed advantage at around 1000 liters per hour, allowing for faster consumption of the anolyte and alleviating the pressure of volume expansion.

[0027] Compared with other existing methods for preparing nickel hydroxide, the preparation process of this application does not require aging or excessively high pH conditions, making the operation simpler, the reaction rate higher, and enabling continuous preparation of nickel hydroxide.

[0028] In this embodiment, the nickel sulfate content in the first anolyte, the second anolyte, and the third anolyte is 50-90 g / L, including but not limited to 50 g / L, 60 g / L, 70 g / L, 80 g / L, and 90 g / L; the pH is 0.5-2, including but not limited to 0.5, 1, 1.5, and 2; the sodium sulfate content is 20-40 g / L, including but not limited to 20 g / L, 25 g / L, 30 g / L, 35 g / L, and 40 g / L; the boric acid content is 2-8 g / L, including but not limited to 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, and 8 g / L; and other components are trace impurities.

[0029] In this embodiment, in step S1, the first complexing agent is ammonia.

[0030] In this embodiment, in step S1, the first alkali is sodium hydroxide.

[0031] In this embodiment, in step S1, the concentration of the first complexing agent in the reaction substrate is 3-6 g / L, including but not limited to 3 g / L, 4 g / L, 5 g / L, 6 g / L, etc.

[0032] In this embodiment, in step S1, the pH of the reaction substrate is 10-11, including but not limited to 10, 10.2, 10.4, 10.6, 10.8, 11, etc.

[0033] In this embodiment, the preparation process of the reaction base liquid in step S1 includes: mixing the first complexing agent, the first alkali and water evenly to obtain the reaction base liquid.

[0034] Preferably, the first complexing agent is added in the form of a solution, and the mass fraction of the first complexing agent solution is 15%-18%, including but not limited to 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, etc.

[0035] Preferably, the first alkali is added in the form of a solution, and the mass fraction of the first alkali solution is 30%-33%, including but not limited to 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, etc.

[0036] Preferably, the first complexing agent, the first alkali and water are mixed evenly by stirring, and the stirring speed is 10-20Hz, including but not limited to 10Hz, 12Hz, 14Hz, 16Hz, 18Hz, 20Hz, etc.

[0037] In this embodiment, in step S2, the second complexing agent is ammonia.

[0038] In this embodiment, in step S2, the mass fraction of the second complexing agent solution is 15%-18%, including but not limited to 15%, 15.5%, 16%, 16.5%, 17%, 17.5%, 18%, etc.

[0039] In this embodiment, in step S2, the second alkali is sodium hydroxide.

[0040] In this embodiment, in step S2, the mass fraction of the second alkaline solution is 30%-33%, including but not limited to 30%, 30.5%, 31%, 31.5%, 32%, 32.5%, 33%, etc.

[0041] In this embodiment, in step S2, the amount of reaction base liquid used is 22%-25% of the volume of the reaction vessel, including but not limited to 22%, 22.5%, 23%, 23.5%, 24%, 24.5%, 25%, etc.

[0042] In this embodiment, in step S2, the feed rate ratio of the first anolyte, the second alkaline solution, and the second complexing agent solution is 1 m / s. 3 / h: (0.25-0.35)m 3 / h: (40-50) L / h, further to 1m 3 / h: 0.3m 3 / h: 45L / h.

[0043] In some specific embodiments of this application, in step S2, the volume of the reactor is 35-40 m³. 3 The feed rate of the first anolyte is 5-7 m / s. 3 / h, including but not limited to 5m 3 / h, 5.5m 3 / h、6m 3 / h, 6.5m 3 / h、7m 3 The feed rate of the second complexing agent solution is 250-300 L / h, including but not limited to 250 L / h, 260 L / h, 270 L / h, 280 L / h, 290 L / h, 300 L / h, etc.; the feed rate of the second alkali solution is 1-2.5 m / h. 3 / h, including but not limited to 1m 3 / h, 1.2m 3 / h, 1.5m 3 / h, 1.8m 3 / h、2m 3 / h, 2.2m 3 / h, 2.5m 3 / h etc.

[0044] In this embodiment, during step S2, the pH of the liquid surface at the top of the reaction vessel is controlled to be 10-11, including but not limited to 10, 10.2, 10.4, 10.6, 10.8, and 11. By controlling the pH of the reaction system at 10-11, this application ensures that nickel ions are basically completely precipitated and that the particle size of nickel hydroxide meets the requirements. If the pH of the reaction system is too low, it will not only result in excessively small nickel hydroxide particle size but also leave a large amount of residual nickel ions in the solution, requiring further treatment of the filtrate to recover the precious nickel, placing significant pressure on wastewater treatment. Conversely, if the pH of the reaction system is too high, it will also result in excessively small reaction product particle size and waste of alkali.

[0045] In this embodiment, during step S2, the total concentration of the first and second complexing agents on the upper liquid surface of the reactor is controlled to be 2-4 g / L, including but not limited to 2 g / L, 2.5 g / L, 3 g / L, 3.5 g / L, and 4 g / L. In the reaction system, the concentration of the second complexing agent is closely related to the particle size of the nickel hydroxide. By controlling the concentration of the second complexing agent in the reaction system within the above-mentioned range, the nickel hydroxide obtained in this invention is more conducive to filtration.

[0046] In this embodiment, during step S2, the reaction temperature is 50-60°C during the stirring reaction. By controlling the reaction temperature at 50-60°C, this application not only ensures that nickel ions are basically completely precipitated, but also reduces damage to equipment (such as automatic control equipment) at high temperatures. Furthermore, the lower temperature results in less steam consumption, thus saving costs.

[0047] In this embodiment, during step S2, the stirring speed is 15-25 Hz, including but not limited to 15 Hz, 17 Hz, 19 Hz, 21 Hz, 23 Hz, and 25 Hz. By controlling the stirring speed within the above range and coordinating it with other reaction conditions (such as pH and ammonia concentration), when the reaction is stable and the solid-liquid mixture gradually reaches the overflow port, the crystal particle size D50 also grows to 15-25 μm. At this point, it flows out of the reaction vessel and enters the filter press for filtration, thus preventing the formation of difficult-to-filter basic carbonates.

[0048] In this embodiment, the target particle size D50 in step S2 is 15-25 μm. By controlling the target particle size D50 within the range of 15-25 μm, this application not only facilitates solid-liquid separation of the nickel hydroxide solution but also facilitates pH adjustment. If the target particle size is too small, nickel hydroxide is prone to penetrating the filter cloth during filtration, and it is difficult for nickel hydroxide to form a filter cake, making sludge removal difficult. If the target particle size is too large, large particles of nickel hydroxide cannot dissolve quickly during pH adjustment, easily leading to pH adjustments exceeding the required range.

[0049] In this embodiment, step S2 specifically includes:

[0050] S21. Add the reaction base liquid to the reaction vessel;

[0051] S22. The first anolyte, the second complexing agent solution, and the second alkali solution are simultaneously and continuously added to the bottom reaction solution from the bottom of the reactor, and the reaction is stirred.

[0052] S23. After the nickel hydroxide reaches the target particle size, it rises to the upper layer of the reactor under stirring and overflows into a filter press for filtration, yielding filtrate and filter cake. In this application, using the above feeding method, if the target particle size is too large, the nickel hydroxide will easily settle to the bottom, making it difficult to overflow the nickel hydroxide slurry from the reactor through stirring.

[0053] This application uses stirring to make the material flow upward. When the reaction is stable, as the solid-liquid mixture gradually reaches the overflow port, the crystal particle size D50 also grows to 15-25um. At this time, it flows out of the reactor and enters the filter press for filtration, without producing hard-to-filter basic carbonates.

[0054] In this application, it should be noted that, in the initial stage of the reaction, due to the limited volume of the reactor, there may be a situation where the crystal particle size D50 has not yet reached 15-25 μm when the solid-liquid mixture gradually reaches the overflow port. At this time, the overflowing nickel hydroxide that has not reached the target particle size can be treated separately. When the particle size D50 reaches 15-25 μm, the reaction is stable. Then, the overflowing nickel hydroxide that has reached the target particle size can be further separated into solid and liquid components to achieve continuous production.

[0055] More specifically, the first anolyte, the second complexing agent solution, and the second alkali solution can be simultaneously added to the bottom of the reaction substrate by extending the feed pipe into the bottom of the reactor.

[0056] In this embodiment, step S2, during the solid-liquid separation process after the nickel hydroxide reaches the target particle size, also includes: continuously feeding the first anolyte, the second alkaline solution, and the second complexing agent into the bottom of the reactor to maintain the reaction temperature and achieve continuous preparation of nickel hydroxide.

[0057] In this embodiment, in step S3, the present invention does not limit the solid-liquid ratio used in the slurrying process. Those skilled in the art can select according to the actual situation, and can use the second anolyte to slurry the filter cake, which is convenient for pipeline transportation and subsequent addition into the reactor.

[0058] In some embodiments of the present invention, in step S3, the nickel content in the nickel hydroxide slurry is 230-300 g / L.

[0059] In this embodiment, in step S4, the mass fraction of the sodium hydroxide solution is 20%-40%, including but not limited to 20%, 25%, 30%, 35%, 40%, etc.

[0060] In this embodiment, in step S4, the concentration of the nickel sulfate solution is 140-150 g / L, including but not limited to 140 g / L, 142 g / L, 145 g / L, 147 g / L, 150 g / L, etc.

[0061] In this embodiment, the sodium ion concentration in the catholyte is 25-35 g / L, the nickel ion concentration is 90-100 g / L, and the pH is 3-3.5.

[0062] In this embodiment, step S4 specifically includes: adjusting the sodium ion concentration, pH and nickel ion concentration of the third anolyte sequentially using sodium hydroxide solution, nickel hydroxide slurry and nickel sulfate solution to obtain the cathode liquid.

[0063] In this application, sodium hydroxide solution is added to the third anolyte to replenish Na ions and achieve Na ion balance; after replenishing Na ions, nickel hydroxide slurry is added to adjust the pH to 3-3.5 to meet the pH requirements of the catholyte; finally, nickel sulfate solution is added to bring the nickel ion content to 90-100 g / L and achieve nickel ion concentration balance.

[0064] Example 1

[0065] This embodiment provides a method for controlling the ion concentration and volume balance in an electrolyte using nickel hydroxide. The raw materials include: 32% liquid alkali (mass fraction) and 16% ammonia (mass fraction); the anolyte composition is: 70 g / L nickel sulfate, pH 1.25, 30 g / L sodium sulfate, 5 g / L boric acid, and other components are trace impurities. The specific steps are as follows:

[0066] (1) Add 8m of pure water 3 Add 200L of ammonia water and 20L of liquid alkali to a volume of 36m³ 3 In the reaction vessel, pure water, ammonia, and liquid alkali were added as needed for fine-tuning to control the pH value at 10.5, the ammonia concentration at 4.5 g / L, and the stirring speed at 15 Hz, thus obtaining the reaction base liquid.

[0067] (2) The anolyte was poured at 6m 3 At a rate of / h, liquid alkali at 1.8m 3 At a rate of 270 L / h, ammonia water was continuously added to the bottom of the reactor. During the reaction, the pH value at the upper liquid surface of the reactor was controlled at 10-11, the ammonia concentration was controlled at 2-4 g / L, the stirring speed was 20 Hz, and the temperature was controlled at 50-60℃. Samples were taken every half hour for testing. After 3.5 hours of reaction, the particle size D50 of nickel hydroxide at the upper liquid surface of the reactor was found to be in the range of 15-25 μm. The nickel hydroxide in the reactor rose to the upper layer of the reactor under the action of stirring and overflowed into the filter press for filtration. The filtrate obtained after filtration (nickel ion concentration of 30-40 mg / L) was discharged as wastewater. The filter cake was washed for 30 minutes before being discharged.

[0068] (3) The filter cake is fed into the slurry tank and mixed with the anolyte at a solid-liquid ratio of 1:4 to obtain a nickel hydroxide slurry with a nickel content of 230-300 g / L.

[0069] (4) Use liquid alkali to prepare the anolyte (actual volume of anolyte 15m³). 3 The reactor volume is 25m³. 3 The sodium ion concentration was adjusted to 25-35 g / L, and then 1 m 3 The pH of the anolyte is adjusted to 3-3.5 by using nickel hydroxide slurry, and finally the nickel ion concentration of the anolyte is adjusted to 90-100 g / L by using a nickel sulfate solution with a concentration of 145 g / L to obtain the catholyte.

[0070] Comparative Example 1

[0071] Compared with Example 1, the only difference is that the pH value of the liquid surface on the upper layer of the reactor is controlled at 8.5-9.5 in step (2). In this comparative example, after 3.5 hours of reaction, the particle size D50 of nickel hydroxide was found to be 5-20 μm; the nickel ion concentration in the filtrate obtained after filtration was 100-200 mg / L.

[0072] Comparative Example 2

[0073] Compared with Example 1, the only difference is that the pH value of the liquid surface on the upper layer of the reactor is controlled at 11-12 in step (2). In this comparative example, after 3.5 hours of reaction, the particle size D50 of nickel hydroxide was detected to be 7-15 μm.

[0074] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, in the system of this application, the pH of the reaction system needs to be strictly controlled. If the pH of the reaction system is too high or too low, it will not be conducive to the complete precipitation of nickel ions and the obtaining of nickel hydroxide that meets the target particle size range.

[0075] Comparative Example 3

[0076] Compared with Example 1, the only difference is that the stirring speed was adjusted to 35 Hz in step (2). In this comparative example, after 3.5 h of reaction, the particle size D50 of nickel hydroxide was found to be 10-20 μm.

[0077] As can be seen from the comparison between Example 1 and Comparative Example 3, the stirring rate needs to be strictly controlled in the system of this application. If the stirring rate is too high, the particle size will reach the overflow port before reaching the target range, and nickel hydroxide that meets the target particle size requirement cannot be obtained.

[0078] Comparative Example 4

[0079] Compared to Example 1, the only difference is that no ammonia was added during the preparation of the reaction substrate or during the reaction process. In this comparative example, after 3.5 hours of reaction, the particle size D50 of nickel hydroxide was measured to be 3-8 μm.

[0080] As can be seen from the comparison between Example 1 and Comparative Example 4, in the system of this application, if ammonia is not added, the particle size of nickel hydroxide will be significantly reduced, which is not conducive to the subsequent solid-liquid separation process and cannot meet the requirements of rapid continuous reaction.

[0081] Performance testing

[0082] Nickel hydroxide was produced according to the reaction conditions of Example 1. The test results of the nickel hydroxide particle size at different times after continuous production following the stabilization of the reaction are shown in Table 1.

[0083] Table 1. Results of nickel hydroxide particle size measured at different time periods under steady-state conditions during continuous reaction.

[0084] Please refer to Table 1. As can be seen from Table 1, during the preparation of nickel hydroxide, the particle size D50 of nickel hydroxide was controlled within 15-25 μm during continuous production at different times after the reaction stabilized. Therefore, the method of this application can control the particle size D50 of nickel hydroxide within 15-25 μm, ensuring stable quality and facilitating subsequent filtration and pH adjustment.

[0085] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Any other corresponding changes and modifications made based on the technical concept of this application should be included within the scope of protection of the claims of this application.

Claims

1. A method for controlling the ion concentration and volume balance in an electrolyte using nickel hydroxide, characterized in that, Includes the following steps: S1. Prepare a reaction base solution containing the first complexing agent and the first base; S2. The first anolyte, the second complexing agent solution, and the second alkaline solution are simultaneously added to the bottom of the reaction substrate and stirred to react. After the nickel hydroxide reaches the target particle size, solid-liquid separation is performed to obtain filtrate and filter cake. S3. After washing the filter cake, it is slurried with a second anolyte to obtain nickel hydroxide slurry. S4. The sodium ion concentration, pH and nickel ion concentration of the third anolyte are adjusted using sodium hydroxide solution, the nickel hydroxide slurry and nickel sulfate solution to obtain the cathode liquid.

2. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that, The first, second, and third anolytes contain 50-90 g / L of nickel sulfate, 20-40 g / L of sodium sulfate, and 2-8 g / L of boric acid. Other components are trace impurities.

3. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that, In the reaction substrate, the first complexing agent is ammonia, the first alkali is sodium hydroxide, the concentration of the first complexing agent is 3-6 g / L, and the pH is 10-11.

4. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that, The second complexing agent is ammonia, and the mass fraction of the second complexing agent solution is 15%-18%; the second alkali is sodium hydroxide, and the mass fraction of the second alkali solution is 30%-33%.

5. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that, The feed rate ratio of the first anolyte, the second alkaline solution, and the second complexing agent solution is 1 m / s. 3 / h: (0.25-0.35)m 3 / h: (40-50)L / h.

6. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that, During the stirring reaction, the volume of the reactor is 35-40 m³. 3 The amount of the reaction substrate is 22%-25% of the volume of the reactor; the feed rate of the first anolyte is 5-7 m / s. 3 The feed rate of the second complexing agent solution is 250-300 L / h, and the feed rate of the second alkaline solution is 1-2.5 m / h. 3 / h.

7. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that, During the stirring reaction, the pH of the liquid surface at the top of the reactor is controlled to be 10-11, the total concentration of the first and second complexing agents is 2-4 g / L, the reaction temperature is 50-60℃, and the stirring speed is 15-25 Hz.

8. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that, The target particle size D50 is 15-25 μm.

9. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that, Step S2 specifically includes: Add the reaction base liquid to the reaction vessel; The first anolyte, the second complexing agent solution, and the second alkaline solution are simultaneously and continuously added to the bottom reaction solution from the bottom of the reactor, and the reaction is stirred. Once the nickel hydroxide reaches the target particle size, it rises to the upper layer of the reactor under stirring and overflows into a filter press for filtration, yielding filtrate and filter cake.

10. The method for controlling ion concentration and volume balance in an electrolyte using nickel hydroxide according to claim 1, characterized in that, Step S4 specifically includes: The sodium ion concentration, pH, and nickel ion concentration of the third anolyte were adjusted sequentially using sodium hydroxide solution, the nickel hydroxide slurry, and nickel sulfate solution to obtain the catholyte; wherein, The catholy solution has a sodium ion concentration of 25-35 g / L, a nickel ion concentration of 90-100 g / L, and a pH of 3-3.5.

Images